Detection Of Internal Defects In Grouting Sleeve And Concrete Based On Piezoceramic Lead Zirconate Titanate Wave And Ultrasonic Imaging

In prefabricated structures,grouting sleeve connections are usually used to connect components due to its good adaptability,short connection length and the limited connecting space between members.However,the non-compactness phenomenon is likely to happen during the casting process of grouting material,concrete and concrete-filled steel tube,which definitely affects the safety and normal performance of structures.Therefore,a new grouting sleeve compactness detection method and a defect imaging algorithm are introduced to carry out internal defect inspections.In addition,several finite element models are simulated to verify the effectiveness and accuracy of the methods mentioned above.The main research contents and innovations of this paper are as follows.(1)Piezoelectric ceramic wave method is introduced and then applied to detect the compactness of the grouting sleeves.Firstly,the piezoelectric is coupled with the sleeve by a use of a finite element model.Then,defects are simulated by cutting a part of grouting materials.Secondly,a parameter analysis is performed for two different internal defects existed in grouting sleeves.Finally,two damage indexes,called wavelet packet energy and first arrival time,are established to detect the compactness of grouting sleeve by using finite element models under healthy and damage cases.(2)A method based on a combination of piezoelectric ceramic and travel time tomography is used to detect the void defects in concrete or concrete-filled steel tubular members.Firstly,the transmitted signal obtained by the finite element analysis is used as the target signal and then the first arrival time of the stress wave is calculated through the peak value method.After that,the velocity field distribution of the measured concrete or concrete-filled steel tube section is computed iteratively by using the travel time tomography algorithm.Secondly,the position and size of the void defects in concrete or concrete filled steel tube are detected according to the variation of the velocity field distributions under various working conditions.Finally,a parameter analysis is employed by finite element simulation to study the effects on the images,which are applied by different defect positions and sizes.The results demonstrate that the method can detect the position and size of internal defects accurately when the defects are located in the middle and approaching of the concrete areas.By contrast,there is a slight deviation in defect localization when the defects are situated in the corners,although the method is capable of detecting the size of defects.